Porous tube injector

ABSTRACT

A fluid injection system for uniformly mixing gases comprising a primary gas conduit; and a plurality of banks of injector tubes with each of said tubes formed with a plurality of radial openings communicating the interior of said tubes with the interior of said conduit, said tubes extending transversely across said conduit with the tubes of each of said banks extending perpendicular to the tubes of each adjacent bank and having the number of tubes in each bank and the size and spacing of said tubes determined so as to provide the maximum tube area possible while maintaining a predetermined minimum Reynolds number of primary gas flowing through said primary gas conduit and ensuring sufficient cooling of said tubes to maintain structural integrity.

United States Patent [1 1 Zajac Sept. 17, 1974 [54] POROUS TUBE INJECTORPrimary Examiner-Robert G. Nilson Inventor: Lawrence J. Zajac, ThousandOaks Attorney, Agent, or Firm-L. Lee Humphries; Robert M. Sperry Calif.

[73] Assignee: Rockwell International Corporation,

El Segundo, Calif. ABSTRACT [22] Filed: Dec. 14, 1972 A fluid injectionsystem for uniformly mixing gases comprising a primary gas conduit; anda plurality of [21] Appl 3l5038 banks of injector tubes with each ofsaid tubes formed with a plurality of radial openings communicating the[52] U.S. Cl. 137/604, 48/180 C, 259/4 interior of said tubes with theinterior of said conduit, [51] Int. Cl. F16k 19/00 said tubes extendingtransversely across said conduit [58] Field of searchn 259/4; 4l180 Cwith the tubes of each of said banks extending perpendicular to thetubes of each adjacent bank and having [56] References Cited the numberof tubes in each bank and the size and UNITED STATES PATENTS spacing ofsaid tubes determined so as to provide the l 178 960 M19 Smith 48mm Cmaximum tube area possible while maintaining a predetermined minimumReynolds number of primary gas FOREIGN PATENTS OR APPLICATIONS flowingthrough said primary gas conduit and ensuring 766,006 l/l957GreatBritain 259/4 sufficient cooling of said tubes to maintainstructural integrity.

7 Claims, 2 Drawing Figures l2 IO -IO -|O lO f a a I x alarm PAIENTEBsmmu H: a q 8 5 H M w/mf H C a a H 5 M mvmvmy s l FIG-2 m r 6 m A D V Q] 6o 6 (m. w 6 m. w r n FIG.

POROUS TUBE INJECTOR BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates to fluid mixing and is particularlydirected to apparatusfor uniformly mixing gases in a combustion chamber.

pssa atiaasiitbslit qr Art It is frequently necessary or desirable tomix gases in a combustion chamber in order to ignite or controlcombustion therein and it is usually desired that such mixing beaccomplished uniformly throughout the combustion chamber. Innumerabledevices have been proposed heretofore for accomplishing such mixing.However, in recent years, interest in non-polluting engines, gas dynamiclasers, and the like, have led to far more stringent requirements foruniformity of mixing and have demanded higher combustion temperaturesthan have been employed previously and it has been found that the priorart fluid injection systems would not satisfy these new requirements.Thus, many of the prior art fluid injection systems have not providedtruly uniform distribution and, hence, have permitted creation of hotspots or, in the case of gas dynamic lasers, have caused non-homogeneousspecies distributions which result in laser beam distortion.Furthermore, these new techniques frequently require temperatures whichwould be above the melting point of conventional materials, whereas thenewer high temperature materials, such as those developed forspacevehicle nose cones, are prohibitively expensive.

BRIEF SUMMARY AND OBJECTS OF INVENTION These disadvantages of the priorart are overcome with the present invention and a fluid injection systemis disclosed which provides truly uniform mixing throughout thecombustion chamber and permits conventional materials to be employed,even where the temperature in the combustion chamber exceeds the meltingpoint of such materials.

The advantages of the present invention are preferably attained byproviding a fluid injection system comprising a primary gas conduit; anda plurality of banks of injector tubes with each of said tubes formedwith a plurality of radial openings communicating the interior of saidtubes with the interior of said conduit, said tubes extendingtransversely across said conduit with the tubes of each of said banksextending perpendicular to the tubes of each adjacent bank and havingthe number of tubes in each bank and the size and spacing of said tubesdetermined so as to provide the maximum tube area possible whilemaintaining a predetermined minimum Reynolds number (e.g., 6000) of theprimary gas flowing through said primary gas conduit. With thisarrangement, transpiration of the injected fluid through the openings inthe injector tubes provides a barrier to the heat flux from the primarygas and serves to protect the structural integrity of the injectortubes.

Accordingly, it is an object of the present invention to provideimproved fluid injection means.

Another object of the present invention is to provide a fluid injectionsystem which assures uniform mixing of the injected fluid with theprimary fluid.

An additional object of the present invention is to provide a fluidinjection system therein the injected fluid forms a heat barrier toprotect the structure of the injector tubes against heat flux from theprimary fluid.

A specific object of the present invention is to provide a fluidinjection system comprising a primary gas conduit; and a plurality ofbanks of injector tubes with each of said tubes formed with a pluralityof radial openings communicating the interior of said tubes with theinterior of said conduit, said tubes extending transversely across saidconduit with the tubes of each of said banks extending perpendicular tothe tubes in each adjacent bank and having the number of tubes in eachbank and the size and spacing of said tubes determined so as to providethe maximum tube area possible while maintaining a predeterminedminimium Reynolds number of the primary gas flowing through said primarygas conduit.

These and other objects and features of the present invention will beapparent from the following detailed description, taken with referenceto the accompanying drawing.

BRIEF DESCRIPTION OF DRAWING FIG. 1 is an end view, partly in section,of a combustion chamber embodying the present invention; and

FIG. 2 is a longitudinal section through the combustion chamberof FIG.1, taken on the line 22 thereof.

DETAILED DESCRIPTION OF INVENTION In that form of the present inventionchosen for purposes of illustration, FIGS. 1 and 2 show a combustionchamber, indicated generally at 2, having a primary gas conduit 4through which primary gas from a suitable supply. is delivered. Aplurality of injector tubes 6 extend transversely across the primaryconduit 4 and are disposed in a plurality of banks, as seen at 8, l0,l2, and 14 in FIG. 2, with the tubes 6 of each bank, such as 10,extending perpendicular to the tubes 6 of each adjacent bank, such asbanks 8 and 12. The injector tubes 6 are formed of a cylindrical mesh ofwire made of heat resistant metal, such as stainless steel or nickel, togive the desired tube porosity.

The diameter and spacing of the tubes 6 and the number of tubes 6 ineach of the banks 8, l0, l2, and 14 may be varied, substantially asdescribed, within the constraint that the total tube area should be madeas large as is possible, while maintaining the structural integrity ofthe tubes 6 and while maintaining a predetermined minimum Reynoldsnumber of the primary gas flowing through the conduit 4. Moreover, theReynolds number of the primary gas flow through conduit 5 should begreater than 200 and preferably greater than 6000..This assures that theflow through the primary conduit will be turbulent and enhances mixingof the primary gas with the secondary gas from the injector tubes 6. Theprovision of the plural banks 8, l0, l2, and 14 of injector tubes 6 alsoserves to promote turbulence and improve mixing of the gases, and it isfound that the degree of turbulence and mixing increases with the numberof such banks provided. On the other hand, the flow of secondary gasthrough the injector tubes 6 forms a heat barrier which serves toprotect the tubes 6 against heat flux from the primary gas and, sincethe volume of the secondary gas to be injected must be divided betweenall of the injector tubes 6, the number of the injector tubes 6 and,thus, the number of banks,

such as banks 8, 10, 12, and 14, must be limited sufficiently to assurethat the flow rate of the secondary gas through each of the injectortubes 6 is adequate to protect the structural integrity of the tubes 6.

In a gas dynamic laser installation embodying the present invention, thediameter of the primary conduit 4 was five inches and the injector tubes6 were onefourth inch diameter tubes formed of a single layer mesh of10-20 gauge stainless steel wire obtained commercially, under thetrademark Rigimesh," from Poraloy Company, El Monte, Calif. Obviously,however, other porous tubes may be employed. Ten of the injector tubes6, spaced on one-half inch centerlines, were disposed transverselyacross the primary conduit 4 in each of four banks, 8, 10, 12, and 14,with the tubes 6 of banks 10 and 14 extending perpendicular to the tubesof banks 8 and 12. The banks 8, l0, l2, and 14 were spaced approximatelyone-half inch apart along the longitudinal axis of the primary conduit4. The temperature of the primary gas (for example, CO N was about5,600F and the secondary gas (for example, N was supplied at atemperature of 80F and at a flow rate approximately twice that of theprimary gas flow rate. With these conditions, the injection system ofthe present invention permitted continuous operation of theinstallation, without failure of the injector tubes 6 and provided adistribution of the secondary gas that corresponded to a standarddeviation of 0.56 percent.

Obviously, numerous variations and modifications may be made withoutdeparting from the present invention. Accordingly, it should be clearlyunderstood that the form of the present invention described above andshown in the accompanying drawing is illustrative only and is notintended to limit the scope of the invention.

What is claimed is:

l. A fluid injection system comprising:

a primary fluid conduit, and

a plurality of porous injector tubes extending transversely across saidconduit with each of said tubes formed of a mesh material having aplurality of openings communicating the interior of said tubes with theinterior of said conduit.

2. The device of claim 1 wherein:

said injector tubes are disposed in a plurality of banks spaced axiallyalong said conduit with each of said banks comprising a plurality ofsaid tubes.

3. The device of claim 2 wherein:

the tubes of each of said banks extend perpendicular to the tubes ofeach adjacent bank.

4. The device of claim 1 wherein:

the number, size and spacing of said tubes is such as to provide themaximum tube area possible while maintaining a predetermined minimumReynolds number of the primary fluid flow through said conduit.

5. The device of claim 1 further comprising:

a primary fluid flowing through said conduit with a Reynolds numbergreater than 200.

6. The device of claim 5 wherein:

the Reynolds number of the primary fluid flow through said conduit isgreater than 6000.

7. The device of claim 5 further comprising:

secondary fluid supplied through said injector tubes at a flow rateapproximately twice that of the flow rate of the primary fluid flowthrough said conduit.

1. A fluid injection system comprising: a primary fluid conduit, and aplurality of porous injector tubes extending transversely across saidconduit with each of said tubes formed of a mesh material having aplurality of openings communicating the interior of said tubes with theinterior of said conduit.
 2. The device of claim 1 wherein: saidinjector tubes are disposed in a plurality of banks spaced axially alongsaid conduit with each of said banks comprising a plurality of saidtubes.
 3. The device of claim 2 wherein: the tubes of each of said banksextend perpendicular to the tubes of each adjacent bank.
 4. The deviceof claim 1 wherein: the number, size and spacing of said tubes is suchas to provide the maximum tube area possible while maintaining apredetermined minimum Reynolds number of the primary fluid flow throughsaid conduit.
 5. The device of claim 1 further comprising: a primaryfluid flowing through said conduit with a Reynolds number greater than200.
 6. The device of claim 5 wherein: the Reynolds number of theprimary fluid flow through said conduit is greater than
 6000. 7. Thedevice of claim 5 further comprising: secondary fluid supplied throughsaid injector tubes at a flow rate approximately twice that of the flowrate of the primary fluid flow through said conduit.